(a) Technical Field of Invention
This invention relates to a method and apparatus for improving the quality of an emulsion explosive composition.
(b) Background of the Art
Commercially available emulsion explosive compositions generally comprise an external or continuous organic fuel phase in which discrete droplets of an aqueous solution of an oxygen-supplying source are dispersed as an internal or discontinuous phase. Such compositions are conventionally described as water-in-oil emulsion explosive compositions, and examples thereof have been described, inter alia, in U.S. Pat. Nos. 3,447,978, 3,674,578, 3,770,522, 4,104,092, 4,111,727, 4,149,916 and 4,149,917.
For certain applications the water content of the oxidiser phase of the emulsion explosive may be completely eliminated or at least reduced to a low level--for example, to less than 4% by weight of the total emulsion composition. Such compositions are conventionally referred to as melt-in-oil or melt-in-fuel emulsion explosives and have been described, inter alia, in U.S. Pat. No. 4,248,644.
The term "emulsion explosive composition" is hereinafter employed to embrace compositions of both the water-in-oil (fuel) and melt-in-oil (fuel) types.
An emulsion explosive composition generally comprises a dispersion of droplets of the oxidiser phase in the continuous phase. These droplets are inherently metastable and exhibit a tendency to crystallise. Growth of the resultant crystals tends to impair the sensitivity to detonation of the emulsion explosive composition. In addition, if the droplets are too large the resultant composition may exhibit poor storage stability and/or poor blasting performance. Such behaviour may also result from the adventitious introduction of extraneous contaminants during production of the explosive composition. Desirably, therefore, the composition should be tested, before use, to assess it potential performance.
Hitherto, such test monitoring as could be performed has been on the basis of periodically extracting samples from the product stream for assessment by microscopic examination to determine droplet size, or by actual test detonation of the samples. At best, such monitoring is intermittent, involves skilled personnel, and entails delay in providing the required assessment. There is therefore a need for a method of assessment which provides a robust, rapid, even instantaneous, simple, and reliable evaluation of potential performance.
We have now devised such a method.